Audience Response Systems (ARS), also known as clickers, are wireless devices commonly used in instruction. The present study explored the effects of ARS on students' performance in an introductory psychology course. The study also described the trajectories of students during the course. Participants in the experimental group used ARS to solve ten true/false questions throughout a three-hour lecture, held once a week. They received feedback immediately after providing an answer. The control group was exposed to the same questions in a paper-and-pencil format at the beginning of each lecture. They received feedback after seven days. The key dependent variable was quantitative performance on course quizzes and exams. Results show that students in the experimental group had statistically significant superior performance compared to the control group. Additionally, analysis of learning trajectories of students in both groups showed that the ARS group gradually progressed to higher performance, whereas the paper-and-pencil group maintained similar performance through the study. These results are discussed within the context of previous findings related to the effects of ARS on instruction. Particularly, we revisit research related to environmental affordances, learning monitoring, motivational factors, feedback density, and ecological validity.